/Engine/Source/Runtime/RHI/Public/RHICommandList.h
void CopyToStagingBuffer ( [FRHIBuffer](API\Runtime\RHI\FRHIBuffer) * SourceBuffer, [FRHIStagingBuffer](API\Runtime\RHI\FRHIStagingBuffer) * DestinationStagingBuffer, uint32 Offset, uint32 NumBytes )